Abstract: A43.00003 : Properties of the BCS-BEC condensate in the BEC regime

Authors:

Jesper Levinsen
Victor Gurarie
(University of Colorado at Boulder)

We study a gas of fermions undergoing a wide resonance s-wave
BCS-BEC crossover, in the BEC regime at zero temperature. We
calculate the chemical potential and the speed of sound of this
Bose-condensed gas, as well as the condensate depletion, in the low
density approximation. We discuss how higher order terms in the low
density expansion can be constructed. We demonstrate that the
standard BCS-BEC gap equation is invalid in the BEC regime and is
inconsistent with the results obtained here. The low
density approximation we employ breaks down in the intermediate
BCS-BEC crossover region. Hence our theory is unable to predict how
the chemical potential and the speed of sound evolve once the
interactions are tuned towards the BCS regime. As a part of our
theory, we derive the well known result for the bosonic scattering
length diagrammatically and check that there are no bound states of
two bosons.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2006.MAR.A43.3